This paper presents a preliminary study on characterizing the synchronized heterogeneous viscous behavior of soft materials upon macroscopic sinusoidal loading. Built upon a polymer-based microfluidic device capable of detecting distributed normal loads at a spatial resolution of 1.5mm, a rigid cylinder probe is employed to exert a macroscopic sinusoidal load on a sample placed on the device. Consequently, the synchronized heterogeneous viscous behavior of a sample translates to sinusoidal distributed loads, which are captured by the device. In a measurement, the input and output signals of a sample are the macroscopic sinusoidal load and the DC voltage outputs of the device, respectively, with the latter being representative of the sinusoidal deflections of a sample along its length. A preliminary data analysis is conducted on the recorded input and output signals to obtain their phase shifts at different frequencies, which are representative of the heterogeneous viscosity of a sample along its length. Several agar and polydimethylsiloxane (PDMS) samples and two animal cartilage tissue samples are prepared and measured. Variations among the measured phase shifts in a sample manifest its structural heterogeneity and demonstrate the feasibility of using the device to characterize the synchronized heterogeneous viscous behavior of soft materials upon macroscopic loading.
